This invention relates to a counter-balance weight for a modular type safety rail and in particular, though not exclusively, to a counter-balance weight and to a modular safety rail assembly suitable for use in providing free-standing roof edge protection.
Modular type safety rail systems are well know and typically comprise straight lengths of metal tubing interconnected by connectors of different types such that, for example, two, three or four way interconnections of horizontally and vertically extending tubes may be achieved.
Tubes serving as vertical posts of a safety rail, and to which horizontally extending tubes are connected, are supported by metal base plates which, in use, rest on the surface of a roof. A flanged mounting socket typically is bolted to an upper surface of the plate, adjacent to one of the shorter edges of the rectangular shape, to provide location for the lower end of a vertical post.
The ability of the free-standing safety rail to avoid toppling when leant on may be achieved by a counter balance weight secured to the end of a spacer tube which, in use, extends horizontally over the roof surface and is secured rigidly to the base plate. This arrangement is particularly suitable if it is not possible or convenient to position a spacer bar to act as a stabiliser member which extends forwards, horizontally, in the direction of potential toppling.
If, however, space permits, a spacer tube may be arranged to extend forwards in the direction of potential toppling so as to act as a stabiliser bar. Optionally in that case the distal end of the stabiliser bar may be provided with a counter balance weight.
Commonly the counter-balance weight comprises a heavy metal plate and an end of a spacer tube is secured to the plate by being received firmly in a horizontally extending sleeve which is either bolted or welded to an upper surface of the plate.
An example of a typical known counter-balance weight is shown in perspective in FIG. 1. The counter-balance weight (10) comprises a rectangular shaped cast iron plate (11) which has welded (13) thereto a tubular sleeve (12) the bore (18) of which is dimensioned to receive the end of a spacer tube. The sleeve bore is provided with a pair of axially spaced screw threaded apertures (14) for receiving grub screws whereby the end of an horizontally extending spacer tube may be secured to the sleeve in known manner.
The aforedescribed construction as shown in FIG. 1 functions satisfactorily in use, but suffers the disadvantage of being costly to manufacture, by virtue for example of the need to weld the sleeve (12) to the plate (11), and, as well as presenting a trip hazard, is not as aesthetically pleasing as may be desirable for some installation locations. Additionally, if the sleeve (12) and plate (11) are pre-assembled by a manufacturer, the maximum possible ratio of weight to container space is not as high as would generally be preferred for reducing shipping costs of bulk supplies from a manufacturer to an importer or other distribution point. That may be a particular disadvantage if it is wished to construct the counter-balance weight from a material having a lower specific gravity than the typical specific gravity of a metal, such as cast iron, because the lighter material necessitates provision of a larger sized weight for the same counter-balance effect.